The fracture toughness of single-crystal graphene and bi-crystal
graphene with different misorientation angles is investigated by
molecular dynamics simulation. We find that the fracture toughness
fluctuates when a crack propagates across the grain boundary. It
indicates that the grain boundary affects the fracture toughness during
the fracture process. The affected region on the graphene is limited to
a small zone around the grain boundary. However, for the complete
tearing-failure case, fracture toughness of bi-crystal graphene is
approximate to that of single-crystal graphene, which implies that the
fracture toughness is not very sensitive to the grain boundary. For
comparison, the tensile fracture simulations of the single-crystal
graphene and bi-crystal graphene are carried out. The results show that
the grain boundaries block the crack propagation and affect fracture
toughness significantly in bi-crystal graphene under tensile force.
Furthermore, we analyze the fracture of a single C-C bond at the crack
tip of single-crystal graphene under tearing load from the atomic view.
We find that the fracture toughness of the single C-C bond occupies
about half of the fracture toughness for the complete failure of the
total single-crystal graphene, and the other half energy distributes in
the rest of the graphene.